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Grey water - not exactly a black & white issue

Article from ebode

We often get asked about the differences between and benefits of various types of grey water re-use systems that we specify for ebode homes, so in this issue we decided to take a look ‘under the surface’ and help our readers get to the bottom of what can sometimes be a bit of a murky issue.

While rain water collection and re-use is reasonably straight forward, the options around grey water are, well, a bit more of a grey area. There are two types of grey water re-use systems available with an ebode home – grey water diversion and grey water recycling. Which of these systems you use (if any) is dependent on your budget, location and, again, local council rules.

A grey water diversion system collects grey water from your washing machine, bath and shower wastes, filters out any hair, lint or solid material, and then diverts the water from the sewage system (where grey water normally goes) to an irrigation system, where it is used to water lawn, trees, flowers and other non-edible plants. If you do not require the grey water for irrigation (e.g., if there is sufficient moisture in the soil due to recent rainfall), it can be manually or automatically set up to redirect the water to the sewage system.

The grey water in a diversion system is used immediately when it is produced, so it does not need to be stored, making it a relatively simple and inexpensive system.
However, there are some limitations to where it can be used – for example, the Kapiti Coast District Council (KCDC) encourages the use of grey water diversion systems, but may decide not to allow one if the water will be discharged within 20 metres of a water body or if the normal water table in your location is less than one metre below the ground level.

While preliminary studies conducted by the KCDC indicate that there is no harm caused by discharging grey water, and in fact it may even benefit the soil, we expect most councils to take a similarly cautious approach until more data is available over a longer period.

A grey water recycling system also collects grey water from your washing machine, bath and shower wastes, but this water is stored in a tank, allowing it to be used when it is needed – for flushing toilets and/or irrigation. Because a tank is needed to store the water, and additional filtering and chemical treatments are required to ensure the stored water does not go smelly, this is a more expensive system than grey water diversion.

While grey water recycling systems are already popular in Australia due to their low and infrequent rainfall, in most areas of New Zealand there is sufficient regular rain to maintain enough rain water for all applications. This may make the recycling of grey water seem a little redundant, as it is cheaper to collect and store rainwater than recycle grey water.

However, with uncertainty over what might happen to the level and frequency of rain here in the future, we think that grey water recycling is likely to become a more common choice – and one which we are already set up to offer to ebode customers.

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